California Department of Fish and Wildlife (CDFW) confirmed that the sea otter known as “Olive” died from a shark bite. Olive was estimated around seven years old. Scientists last spotted Olive alive on Feb. 15, 2015, and then a private citizen reported discovering her dead on the beach March 22. After her rescue and rehabilitation in 2009, Olive became an ambassador for her species and other oil-affected wildlife. CDFW documented her activities on the “Olive the Oiled Otter” Facebook page, where more than 5,000 people followed her.
“Her carcass was in an advanced state of decomposition, but we found wounds consistent with a shark bite,” said Colleen Young, CDFW wildlife biologist, who collected Olive’s carcass for examination. “We also found a large, serrated tooth fragment from a white shark in one of the wounds, which confirmed our suspicions that she was bit by a shark.”
Although the level of decomposition made it difficult to assess thoroughly the health of her tissues and organs, CDFW scientists determined that she had good body condition, and all organs appeared healthy. Olive’s wounds showed no signs of healing, indicating that she died quickly after the fatal bite.
“Shark bites are currently the leading cause of mortality of southern sea otters, and we’ve documented an alarming increase in shark bite mortality over the last five years,” said Young. White sharks are not known to consume sea otters, but otters rarely survive the bite.
While shark bites as a cause of death in sea otters has increased, several other factors can cause sea otter deaths, including: biotoxins (especially domoic acid and microcystin), bacterial infections, protozoal infections, other parasite infections, direct human-related causes (gun shots, boat strikes, entanglements), intraspecific trauma (trauma caused by other otters, including during mating), viruses, starvation and emaciation, and occasionally tumors or other issues. Typically, more than one factor contributes to a sea otter’s death. Male otters typically live into their early teens and females into their mid-teens in the wild. Sea otters in captivity generally live longer.
“Although some causes of death are natural, many are anthropogenic [human-caused] and we have the ability to mitigate them,” said Young. “Restoring and protecting the marine habitats of sea otters, as well as habitats located upstream and inland, can help reduce these threats to sea otters. Land-sea pollution is a bigger problem for sea otters than most people realize.”
Olive first made headlines in Feb 2009, when she stranded alive on Sunset State Beach covered in thick, tarry oil. Estimated to be about a year old at the time, the youngster had been fouled by oil from a natural seep off the California coast. A team from CDFW, the Marine Mammal Center (TMMC), the Monterey Bay Aquarium (MBA), and UC Santa Cruz (UCSC) Long Marine Lab rescued, washed and rehabilitated her. Olive recovered in a pool of warm softened fresh water according to a new protocol developed by CDFW, UCSC, MBA, and the UC Davis Oiled Wildlife Care Network (OWCN), which drastically improved her recovery time. After several weeks, Olive’s fur was back to normal, and she had reached a normal weight. The team equipped her with a VHF transmitter and colored flipper tags so she could be monitored after she returned to the wild.
CDFW monitored Olive intermittently after her release in April 2009 through December 2011. Starting in January 2012, scientists monitored her more on a weekly basis to document her health and reproductive success. She was successfully captured for a health exam in July 2012 that revealed her blood values and other health parameters were within normal limits for a healthy, wild sea otter. She was pregnant at the time of the exam and gave birth to her first known pup in late August or early September 2012. Olive weaned that pup, and since then gave birth to, and successfully weaned two additional pups, a great contribution to the southern sea otter population, which is listed as Threatened under the Endangered Species Act.
Although Olive’s death saddens many of the researchers and public who have followed her over the years, her life provided a tremendous opportunity to learn a great deal about otters.
“We owe Olive a lot because she gave us a lot. She showed us that with our newer methods of washing, rinsing and recovering oiled sea otters, even very sick, starved and badly tarred sea otters could be saved,” said David Jessup, the retired CDFW wildlife veterinarian who oversaw Olive’s initial washing and rehabilitation. “She showed us that oiled sea otters can go on to live normal healthy lives, have healthy pups, be good mothers and then die of natural causes.”